Method and structure for hydrogenation of silicon substrates with shaped covers

• US 8,153,887 B2
• Filed: 09/10/2007
• Issued: 04/10/2012
• Est. Priority Date: 09/11/2006
• Status: Expired due to Fees

• Current Assignee: Silicon China (HK) Limited
• Original Assignee: Silicon China (HK) Limited
• Inventors: Chan, Yick Chuen, Cheung, Nathan W., Wong, Man, Chan, Chung, Ho, Pui Yee Joan
• Primary Examiner(s): Ridley, Basia
• Assistant Examiner(s): Ayad, Tamir
• Application Number:
  US11/852,856
• Publication Number:
  US 20080092948A1
• Time in Patent Office: 1,674 Days
• Field of Search: 136/255, 136/252, 136/261, 136/265, 136/264, 136/262, 136/260, 156/196, 156/247, 438/72, 257/E31
• US Class Current: 136/255
• CPC Class Codes: H01L 31/02168 the coatings being antireflective or having enhancing optical properties for the solar cells
• CPC Class Codes: H01L 31/02363 of the semiconductor body itself, e.g. textured active layers
• CPC Class Codes: H01L 31/0352 characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
• CPC Class Codes: H01L 31/04 adapted as photovoltaic [PV] conversion devices testing thereof during manufacture H01L22/00; testing thereof after manufacture H02S50/10
• CPC Class Codes: H01L 31/18 Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y10T 156/1002 with permanent bending or reshaping or surface deformation of self sustaining lamina

Abstract

Method and structure for hydrogenation of silicon substrates with shaped covers. According to an embodiment, the present invention provides a method for fabricating a photovoltaic material. The method includes providing a semiconductor substrate. The method also includes forming a crystalline material characterized by a plurality of worm hole structures therein overlying the semiconductor substrate. The worm hole structures are characterized by a density distribution from a surface region of the crystalline material to a defined depth within a z-direction of the surface region to form a thickness of material to be detached. The method further includes providing a glue layer overlying a surface region of the crystalline material. The method includes joining the surface region of the crystalline material via the glue layer to a support substrate.

Claims

1. A method for fabricating a photovoltaic material comprising:

providing a semiconductor substrate;

forming a first layer and a second layer of porous semiconductor crystalline material on the semiconductor substrate, both layers comprised of a plurality of wormhole structures, wherein density distribution of the wormhole structures in the first layer ranges from 10/cm³ to 10¹⁰/cm³ and density distribution of the wormhole structures in the second layer ranges from 10¹⁰/cm³ to 10²⁰/cm³, wherein the second layer is in between the first layer and the substrate, wherein detachment from the semiconductor substrate occurs at the second layer;

subjecting the porous semiconductor crystalline material comprised of wormhole structures to a hydrogen plasma species to passivate the semiconductor crystalline material to reduce an electron-hole recombination process;

forming a joining layer over a surface region of the porous semiconductor crystalline material comprised of wormhole structures;

joining the surface region of the porous semiconductor material to a support;

delaminating a portion of the porous semiconductor crystalline material from the semiconductor substrate while the portion of the porous semiconductor crystalline material remains joined to the support via the joining layer, the portion of the porous semiconductor crystalline material forming a continuous layer of porous semiconductor crystalline material comprised of wormhole structures, the delaminating creating a new surface of the porous semiconductor crystalline material, the new surface forming a light-incident surface of the photovoltaic material, the new surface having a texture configured to capture light incident on the surface of the photovoltaic material and characterized by cleaved wormhole structures, the cleaved wormhole structures forming a surface roughness of greater than 10 nanometers to cause less than about 25% reflection from a total amount of irradiating incident light in a wavelength ranging from about 0.1 micron to about 5 microns;

forming a substantially transparent incident light-trapping cover layer having a cover refractive index attached to the new surface, the cover layer having plural facets including wedge angles between adjacent facets configured to reflect incident light reflected from the new surface back into the new surface, the light-trapping cover layer having a thickness of about 1 micron to about 100 microns.

2. The method of claim 1 wherein the forming a cover layer comprises:

depositing a thickness of dielectric material over the new surface region of the delaminated portion of the thickness of the crystalline material, and forming facets on a top portion of the thickness of the dielectric material.

3. The method of claim 2 wherein the facets include a first facet and a second facet, the first facet and the second facet sharing a wedge, the wedge having a total internal reflection angle.

4. The method of claim 2 wherein the depositing comprises physical vapor deposition.

5. The method of claim 2 wherein the forming facets comprises performing directional etching on the top portion of the thickness of the dielectric material.

6. The method of claim 2 wherein the facets include a first facet and a second facet, the first facet and the second facet sharing a wedge angle for light trapping, the wedge angle being associated with the cover refractive index.

7. The method of claim 2 wherein the forming wedge facets comprises determining at least a first angle for a maximum amount of light trapping.

8. The method of claim 1 wherein the forming a cover layer comprises providing a thickness of polymer material and molding the thickness of polymer material to form wedge facets on a top portion of the thickness of polymer material.

9. The method of claim 1 wherein the forming a cover layer comprises providing a thickness of polymer material and pressing the thickness of polymer material to form wedge facets on a top portion of the thickness of polymer material.

10. The method of claim 1 wherein the forming a cover layer comprises:

providing a thickness of glass material;

shaping a top portion of the thickness of glass material to form wedge facets on a top portion of the thickness of the glass material.

11. The method of claim 1 wherein the cover layer is attached to the thickness of the crystalline material by an adhesive.

12. The method of claim 1 wherein the cover layer comprises dielectric material.

13. The method of claim 1 wherein the cover layer comprises polymer material.

14. The method of claim 1 wherein the cover layer comprises glass material.

15. The method of claim 1 wherein the semiconductor substrate comprises silicon.

16. The method of claim 1 wherein the semiconductor substrate comprises single crystal silicon, silicon germanium, gallium arsenide, Group II/VI, or Group III/V materials.

17. The method of claim 1 wherein the forming of the crystalline material characterized by the plurality of worm hole structures comprises electrochemical etching a portion of a thickness of the semiconductor substrate to form the thickness of material to be detached and to form the interface between the thickness of material and the remaining portion of the semiconductor substrate.

18. The method of claim 1 wherein the delaminating comprises subjecting the portion of the crystalline material to a thermal treatment process.

19. The method of claim 1 wherein the delaminating comprises subjecting the portion of the crystalline material to a mechanical prying process.

20. The method of claim 1 wherein the delaminating comprises subjecting the portion of the crystalline material to electromagnetic radiation.

21. The method of claim 1 wherein the delaminating comprises subjecting the portion of the crystalline material to a chemical process.

22. The method of claim 1 wherein the delaminating comprises subjecting the portion of the crystalline material to an energy to cause the delaminating.

23. The method of claim 1 wherein the glue layer is selected from spin on glass, a eutectic material, a polymer, or a metal layer.

24. The method of claim 1 wherein the worm hole structures comprise a characteristic dimension ranging from about 1 nanometer to about 1 micron.

25. The method of claim 1 further comprising forming one or more P type and N type junctions on a portion of the crystalline material.